Mix the beef, cumin, paprika, salt and plenty of freshly ground black pepper together in a bowl. Divide the mince mixture into 8 portions and press each portion firmly onto flat skewers, each one around 10–12cm long. Preheat the Retigo combi oven with Retigo express grill inside on hot air mode 50%, 250C, after preheating set the temperature to 195C and grill the lightly oiled kebabs for 8 minutes. Add the onion wedges to the griddle for the last 3 minutes of the cooking time and griddle until lightly charred. Serve with a dip to your choice.